From U.K. patent specification 1,370,546 a heart assist catheter pump is known which includes a catheter having a distal end for insertion from the aorta past the aortic valve into the left ventricle. The distal end has inlet openings. Spaced from the distal end, the catheter has outlet openings and a set of check valves for allowing outward flow. Valves are provided for controlling the direction of the flow. A fluid displacement device communicating with the proximal end of the catheter alternatingly generates a suction causing blood to be withdrawn from the left ventricle into the catheter and to the displacement device and an excess pressure causing blood to be expelled from the catheter downstream side of the aortic valve.
Later catheter pumps for assisting the left ventricle heart by pumping blood from a distal catheter tip portion to an outlet spaced from the distal tip are disclosed in U.S. Pat. Nos. 3,995,617, 4,014,317, 6,007,479 and 6,398,714. U.S. patent application 2002/0123661 discloses the use of a catheter pump with an inlet distally from the outlet for causing blood pressure pulsations in the aorta, for instance in addition to a non-pulsatile flow maintained by a heart lung machine.
However, for some clinical applications, blood is pumped through the catheter in opposite direction, i.e. from an inlet in a position spaced from the distal tip towards the distal tip.
One example of such a clinical application is assisting the function of the right ventricle of the heart. Devices for assisting this function are known as Right Ventricular Assist Devices (RVAD). An example of a RVAD in the form of catheter pump is disclosed in U.S. Pat. No. 4,985,014 in which the catheter is a double lumen or coaxial channel catheter and the pump a roller pump. Examples of single lumen catheter pumps for use as a RVAD are disclosed in International patent applications WO99/26677 and WO00/13736.
Another example of a clinical application in which blood is pumped from an inlet in a position spaced from the distal tip to the distal tip is proposed in International patent application WO99/26676. According to this document, the catheter is inserted through an incision in the left ventricle and advanced until the distal end is in the aorta while a more proximal portion including an inlet is in the left ventricle. The catheter then functions as a left ventricular assist device.
An important problem associated with pumping blood is that blood cells are easily damaged in the valves, where the blood experiences abrupt changes in either the rate or direction of its flow under influence of mechanical forces and that, at the valves, the risk of thrombosis is increased. In International patent application WO 98/57698, the problem of blood cell damage is addressed and special valves are proposed. U.S. Pat. No. 6,398,714 discloses to reduce the risk of thrombosis by providing a single valve that alternatingly closes off a passage in the wall of the catheter and the lumen of the catheter. However, these solutions are still relatively complex and specifically suitable for catheters in which blood is displaced away from the tip towards an outlet more spaced from the tip than the inlet.